A sump pump is placed in a hole that fills with water. When the float rises on rising water it trips a sump pump switch which operates by a fast action, over center mechanism. The water rises, the pump comes on, the water goes out, the float falls and the switch turns off. It is damp in the hole, and the switch gets quite hot when a lot of pumping is done. It is bad news if the switch fails to function.
When any electrical contacts come together, the best design provides a skidding motion and there is some compliance in one of the contacts so there is a way to take up wear over time. The moving contact of this switch has a lot of spring compliance to give the good rocking, sliding, contact cleaning, motion; but how that contactor was mounted created problems. The bad old contactor was a flat part bent into a hairpin spring that slipped over a fiber contact carrier. A lanced barb in the middle of the hairpin kept the contact from sliding off of the carrier. If the hairpin was too tight, or the barb too tall, the hairpin spring would take a set when installed, and the resulting looseness on the carrier reduced its service life. If it was too loose, same problem. Unfortunately, the contact was hard to make and keeping that hairpin formed well was not easy. After years of struggling with suppliers to get the parts right, I redesigned the contact to eliminate the hairpin altogether. Instead of the spring being clipped onto the carrier, I created two hooked arms to pull the contactor off from the closed position. Check out the patent that was awarded for this to see details of the improved design. The new design was tested for a million cycles and passed with no problems. |